I'm not sure why you want to do it, but based on MSDN, you can do that.

Out and Ref Parameters.

In most cases, you can use in parameters (ByVal in Visual Basic) and out and ref
parameters (ByRef in Visual Basic). Because both out and ref parameters indicate
that data is returned from an operation, an operation signature such as the following
specifies that a request/reply operation is required even though the operation signature returns void.